The present invention relates to electrophotographic developing apparatus wherein carriers of latent images are contacted by a liquid developer, especially to apparatus for developing latent images on dielectric receptor sheets which were exposed to object-modulated X-rays, for example, in an ionography imaging chamber. More particularly, the invention relates to improvements in developing apparatus of the type disclosed in commonly owned German Offenlegungsschrift No. 2,545,333 published Apr. 22, 1976.
When a dielectric receptor sheet is exposed to radiation in an ionography imaging chamber, the charge of the latent image is substantially lower than the charge of a latent electrostatic image which is obtained by an electrophotographic technique. Such lower charges are satisfactory because, and as disclosed in the aforementioned German publication, the developing electrodes (which are interrupted by paths for a flowing liquid developer) can be placed into close or immediate proximity of the dielectric receptor sheet which carries the latent image. As a rule, the paths for liquid developer are narrow so that the developer is free of turbulence and, by proper selection of the speed of the developer, the receptor sheet is contacted by a body of liquid which forms a laminar flow. Consequently, the developing apparatus is highly sensitive and can accurately reproduce half-tone images. Moreover, one can eliminate the so-called edge effect which is a phenomenon that cannot be avoided when a latent image is developed in an electrophotographic developing apparatus. The term "edge effect" is intended to denote that only the outline of a dark area is visible, i.e., the major part of the dark area is light grey or white, the same as the region immediately surrounding the dark area.
As a rule, the edge effect is a highly undesirable phenomenon which is an unavoidable by-product of conventional electrophotographic developing procedures. On the other hand, such edge effect, or a certain amount of edge effect, may be desirable when the image of an X-rayed object is examined by a technician, nurse or physician.